It is difficult to put into words, but the concept of void has long been a favorite of mine.
As a child, I would read Norse mythology. The Norse creation story takes place in Ginnungagap, an utterly endless void that separated the ‘worlds’ of fire (Muspelheim) and ice (Nifleheim). Even as a child, the paradox of an endless void flanked by other realms enticed and confused me. (It should be noted that other sources state Ginnungagap is just incredibly large rather than endless.)
At Sunday School, we had a class about heaven where we all shared the first question we would ask God. Mine was, “Can you show me the void before the universe existed?”
But that void predates even Genesis 1:2.
The Douay-Rheims renders the verse:
In the beginning God created heaven, and earth. And the earth was void and empty, and darkness was upon the face of the deep; and the spirit of God moved over the waters. Genesis 1:1-2
Void simply refers to the earth being empty, without feature. I would imagine it looked like a big ball of very wet mist. Half the mist was then separated into the heavens and the other half condensed into the oceans. But who knows?